The present disclosure relates, generally, to a method of communicating between electronic devices, and more particularly, to a network assignment procedure of a mobility management entity (MME), a gateway, and a user equipment (UE), for communicating between heterogeneous networks in a wireless communication system.
In order to meet the increasing demand for wireless data traffic, i.e., since the commercialization of 4th generation (4G) communication systems, 5th generation (5G) or pre-5G communication systems are currently being developed; the 5G or pre-5G communication systems are sometimes referred to as a beyond 4G network communication system or post long-term evolution (LTE) system.
The international communication organizations including international telecommunication unit (ITU) and 3rd Generation Partnership Project (3GPP) have proposed three uses of the 5G communication system: enhanced mobile broadband (eMBB), ultra-reliable and low latency communications (URLLC), and massive machine type communication (mMTC).
Currently, the 5G communication system is considering implementation using millimeter wave (mmW) frequency bands (e.g., 60 GHz bands) to accomplish higher data rates. In order to increase the propagation distance by mitigating propagation loss in the 5G communication system, various techniques such as beamforming, massive multiple-input multiple output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large-scale antenna are being considered as possible solutions.
Other techniques, such as evolved small cells, advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device to device (D2D) communications, wireless backhauls, moving networks, cooperative communications, coordinated multi-points (CoMP)s, interference cancellations, hybrid frequency shift keying (FSK), quadrature amplitude modulation (QAM), sliding window superposition coding (SWSC), advanced coding modulation (ACM), filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) are also being considered for enhancement of network performance of the 5G communication system.
Additionally, stability of the 5G communication system is not easy to achieve when compared with the 4G communication systems, because of the need to support a data rate that is a few dozen multiples of the legacy 4G communication systems.
For example, when using a beamforming technique to achieve the high data rate required by the 5G communication system, if a line-of-sight (LOS) path cannot be maintained when communicating between a base station and a terminal, instantaneous performance degradation and radio link failure may result. In addition, there is likely to be a lack of coverage (or an abundance of 5G coverage holes) as a result of not having sufficient 5G base stations to cover an entire nation.
In view of the foregoing, there exists a need of a method for operating 5G communication networks with legacy 4G communication networks, i.e., a handover method. For example, it may prove advantageous for a 4G base station to be able to communicate with a terminal that is leaving a 5G communication area and entering a non-5G communication service area.